1. Field of the Invention
This invention relates generally to water purification mechanisms and more particularly to a reverse osmosis water purification system for use in limited water supply installations.
2. Description of the Prior Art
The purification of water by reverse osmosis is an old and well known technology which is being used considerably more today than it was in the past due to increasing drinking water problems resulting from pollution, and the like. The increasing usage of this old technology has resulted in the development and refinement of systems which are economically and technically feasible for use in domestic and similar applications.
Water purification by reverse osmosis, as is well known in the art, takes time and therefore is unsuited for use on a direct as needed, or demand basis. In other words, in order for a water purification reverse osmosis apparatus to be practical, the apparatus will operate until a predetermined quantity of pure water is produced and that water is stored for use when a demand occurs. When a demand occurs, the reverse osmosis apparatus will resume operation to replace the amount depleted from the stored supply by the demand.
A particular prior art reverse osmosis water purification and storage apparatus currently being used employs a special diaphragm-type hydro-pneumatic storage tank into which the purified water from a reverse osmosis unit is stored. The special tank is provided with a diaphragm to divide it into a water storage compartment and a pre-pressurized air compartment. Pure water from the reverse osmosis unit is directed into the water storage compartment and, by diaphragm action, will compress the air in the pre-pressurized air compartment. When a demand for pure water occurs, the compressed air in the air compartment will exert a force in the diaphragm causing the water in the storage compartment of the tank to flow under the influence of that force through the plumbing line to the open fixture, usually a faucet.
In order for a reverse osmosis unit to function properly, there must be a differential pressure across the reverse osmosis membrane. In view of this requirement, it is essential that the water pressure in the water storage compartment of the special tank of the above described prior art apparatus not be allowed to approach input line pressure. If this is allowed to occur, the differential pressure across the reverse osmosis membrane will fall below a minimum value and the pure water production rate of the reverse osmosis unit as well as the purity of the water will fall below acceptable levels.
When water is being purified by reverse osmosis, it will, in addition to producing highly purified water, produce a considerable amount of waste water as is well known in the art. This production of waste water has kept the use of the reverse osmosis water purification technology from being used whenever the supply of water to be purified is limited for whatever reason.
For example, in self contained motor homes, recreational vehicles, boats and the like, it is a common practice to carry water in a supply tank on board the vehicle. Water from a known source of potable water is placed in the supply tank and is used for multiple purposes such as flushing toilets, washing dishes, bathing, and of course, drinking and cooking. In that potable water is not always available at all locations where the above mentioned types of vehicles may travel or be used, the water in the supply tank is used very carefully and conserved whenever possible. Due to this, reverse osmosis water purification systems have heretofore not been used in limited water supply situations because of the inherent, production of waste water in such systems.
Therefore, a need exists for a new and useful reverse osmosis water purification system for use in limited water supply installations.